Semiconductor device and manufacturing method thereof

ABSTRACT

A TFT is manufactured using at least five photomasks in a conventional liquid crystal display device, and therefore the manufacturing cost is high. By performing the formation of the pixel electrode  127 , the source region  123  and the drain region  124  by using three photomasks in three photolithography steps, a liquid crystal display device prepared with a pixel TFT portion, having a reverse stagger type n-channel TFT, and a storage capacitor can be realized, FIG.  2.

DETAILED DESCRIPTION OF THE INVENTION Technical Field to which theInvention Belongs

The present invention relates to a semiconductor device having a circuitcomprising a thin film transistor (hereafter referred to as TFT), and toa method of manufacturing thereof. For example, the present inventionrelates to an electro-optical device, typically a liquid crystal displaypanel, and to electronic equipment loaded with this type ofelectro-optical device as a part.

Note that, throughout this specification, semiconductor device denotes ageneral device which can function by utilizing semiconductorcharacteristics and that the category of semiconductor devices includeselectro-optical devices, semiconductor circuits, and electronicequipment.

In recent years, techniques of structuring a thin film transistor (TFT)by using a semiconductor thin film (with a thickness on the order ofseveral nm to several hundred of nm) formed over a substrate having aninsulating surface have been in the spotlight. The thin film transistoris being widely applied in an electronic device such as an IC or anelectro-optical device, and in particular, its development as aswitching element of an image display device has been proceedingrapidly.

Conventionally, a liquid crystal display device is known as an imagedisplay device. Active matrix liquid crystal display devices have comeinto widespread due to the fact that, compared to passive liquid crystaldisplay devices, a higher precision image can be obtained. By drivingpixel electrodes arranged in a matrix state in the active matrix liquidcrystal display device, a display pattern is formed on a screen in anactive matrix liquid crystal display device. In more detail, by applyinga voltage between a selected pixel electrode and an opposing electrodecorresponding to the pixel electrode, optical modulation of a liquidcrystal layer arranged between the pixel electrode and the opposingelectrode is performed, and the optical modulation is recognized as adisplay pattern by an observer.

The use of this type of active matrix liquid crystal display device isspreading, and along with making the screen size larger, demands forhigher precision, higher aperture ratio, and higher reliability areincreasing. Further, at the same time, demands are increasing forimproving productivity and lowering costs.

Conventionally, an amorphous silicon film is ideally used as anamorphous semiconductor film because of the capability of forming it ona large surface area substrate at a low temperature equal to or lessthan 300° C. Further, a reversed stagger type (or bottom gate type) TFThaving a channel forming region formed by an amorphous semiconductorfilm is often used.

Problem to be Solved by the Invention

Conventionally, the production costs have been high in order tomanufacture a TFT on a substrate with a technique of photolithographyusing at least 5 photomasks for an active matrix type liquid crystaldisplay device. In order to improve productivity and yield, reducing thenumber of steps is considered as an effective means.

Specifically, it is necessary to reduce the number of photomasks neededto manufacture the TFT. The photomask is used in a photolithographytechnique in order to form a photoresist pattern, which becomes anetching process mask, over the substrate.

By using one photomask, there are applied with steps such as applyingresist, pre-baking, exposure, development, and post-baking, and inaddition, steps of film deposition and etching, resist peeling,cleaning, and drying are added before and after these steps. Therefore,the entire process becomes complex, which leads to a problem.

Further, static electricity is generated by causes such as frictionduring manufacturing steps because the substrate is an insulator. Shortcircuits develop at an intersection portion of wirings formed on thesubstrate when static electricity is generated, and then deteriorationor breakage of the TFT due to static electricity leads to display faultsor deterioration of image quality in liquid crystal display devices. Inparticular, static electricity develops during rubbing in the liquidcrystal aligning process performed in the manufacturing steps, and thisbecomes a problem.

The present invention is for solving such problems, and an object of thepresent invention is to reduce the number of steps for manufacturing aTFT, and to realize a reduction in the production cost and animprovement in yield for a semiconductor device typified by an activematrix type liquid crystal display device.

Further, an object of the present invention is to provide a structureand a method of manufacturing the structure for resolving the problemsof damage to the TFT and deterioration of TFT characteristics due tostatic electricity.

Means for Solving the Problem

In order to solve the above problems, in the present invention, first, agate wiring line is formed by a first photomask.

Next, a gate insulating film, a non-doped amorphous silicon film(hereinafter referred to as a-Si film), an amorphous silicon filmcontaining an impurity element to give an n-type conductivity(hereinafter referred to as n⁺a-Si film), and a conductive film arecontinuously formed.

Next, a gate insulating film, an active layer comprising the a-Si film,a source wiring line (including a source electrode), and a drainelectrode are formed through patterning by a second photomask.

Thereafter, after a transparent conductive film is formed, a pixelelectrode made of the transparent conductive film is formed by a thirdphotomask, and further, at the same time that a source region and adrain region comprising the n⁺a-Si film are formed, a part of the a-Sifilm is removed.

By adopting such structure, the number of photomasks used in aphotolithography technique can be made three.

Further, the source wiring is covered by a transparent conductive filmcomprising the same material as the pixel electrode, a structure whichprotects the entire substrate from eternal static electricity or thelike is used. Furthermore, a structure in which a protecting circuit isformed using the transparent conductive film may also be used. Thegeneration of static electricity due to friction between productionequipment and the insulating substrate can be prevented duringmanufacturing processing by using this type of structure. In particular,the TFTs can be protected from static electricity generated during aliquid crystal alignment process of rubbing performed duringmanufacturing steps.

A structure of the present invention disclosed in this specification is:

a semiconductor device possessing a gate wiring, a source wiring, and apixel electrode, having:

the gate wiring 102 formed on an insulating surface;

the insulating film 110 formed on the gate wiring;

the amorphous semiconductor film 122 formed on the insulating film;

the source region 123 and the drain region 124 formed on the amorphoussemiconductor film;

the source wiring 125 or the electrode 126 formed on the source regionor the drain region; and

the pixel electrode 127 formed on the electrode;

characterized in that:

one end surface of the drain region 124 or the source region 123reversed corresponds with an end surface of the insulating film 110, anend of the amorphous semiconductor film 122 and an end surface of theelectrode 126.

Further, another structure of the present invention is:

a semiconductor device possessing a gate wiring, a source wiring, and apixel electrode, having:

the gate wiring 102 formed on an insulating surface;

the insulating film 110 formed on the gate wiring;

the amorphous semiconductor film 122 formed on the insulating film;

the source region 123 and the drain region 124 formed on the amorphoussemiconductor film;

the source wiring 125 or the electrode 126 formed on the source regionor the drain region; and

the pixel electrode 127 formed on the electrode;

characterized in that:

one end surface of the drain region 124 or the source region 123reversed corresponds with an end surface of the insulating film 110, anend surface of the amorphous semiconductor film 122 and an end surfaceof the electrode 126; and

the other end surface of the drain region 124 or the source region 123reversed corresponds with an end surface of the pixel electrode 127 andthe other end surface of the electrode 126.

Further, each of the above structures is characterized in that thesource region and the drain region comprises an amorphous semiconductorfilm containing an impurity element which imparts n-type conductivity.

Still further, each of the above structures is characterized in that theinsulating film, the amorphous semiconductor film, the source region,and the drain region are formed in succession without exposure to theatmosphere.

In addition, each of the above structures is characterized in that theinsulating film, the amorphous semiconductor film, the source region, orthe drain region is formed by a sputtering method.

Additionally, each of the above structures is, as shown in FIG. 2(D),characterized in that the source region 123 and the drain region 124 areformed by using the same mask as that of the amorphous semiconductorfilm 122 and the electrode 126. Moreover, it is characterized in thatthe source region and the drain region are formed by using the same maskas that of the source wiring 125.

Further, each of the above structures is, as shown in FIG. 2(D),characterized in that the source region 123 and the drain region 124 areformed by using the same mask as that of the source wiring 125 and thepixel electrode 127.

In addition, in each of the above structures, by etching process shownin FIG. 2(D), there is provided a structure in which, in the amorphoussemiconductor film, the film thickness in a region that contacts withthe source region and the drain region is formed thicker than the filmthickness in a region between a region that contacts with the sourceregion and a region that contacts with the drain region, that is, achannel etch type bottom gate structure.

Besides, the structure of the invention for realizing the aboveconstruction is a method of fabricating a semiconductor device,characterized by comprising:

a first step of forming a gate wiring line 102 by using a first mask;

a second step of forming an insulating film 104 covering the gate wiringline;

a third step of forming a first amorphous semiconductor film 105 on theinsulating film;

a fourth step of forming a second amorphous semiconductor film 106containing an impurity element to give an n-type conductivity on thefirst amorphous semiconductor film;

a fifth step of forming a first conductive film 107 on the secondamorphous semiconductor film;

a sixth step of forming a wiring line 116 (a source wiring line and anelectrode) by selectively removing the insulating film 104, the firstamorphous semiconductor film 105, the second amorphous semiconductorfilm 106, and the first conductive film 107 by using a second mask;

a seventh step of forming a second conductive film 118 being in contactwith and overlapping with the wiring line 116 (the source wiring lineand the electrode); and

an eighth step of forming a source region 123 and a drain region 124comprising the second amorphous semiconductor film, and a pixelelectrode 127 made of the second conductive film by selectively removinga part of the first amorphous semiconductor film 112, the secondamorphous semiconductor film 114, the first conductive film 116, and thesecond conductive film 118 by using a third mask.

Besides, in the above structure, it is characterized in that formationis continuously made without being exposed to the air from the secondstep to the fifth step.

Besides, in the above respective structures, it is characterized in thatformation is continuously made in the same chamber from the second stepto the fifth step.

Besides, in the above respective structures, the insulating film may beformed by a sputtering method or a plasma CVD method.

Besides, in the above respective structures, the first amorphoussemiconductor film may be formed by a sputtering method or a plasma CVDmethod.

Besides, in the above respective structures, the second amorphoussemiconductor film may be formed by a sputtering method or a plasma CVDmethod.

Besides, in the above respective structures, it is characterized in thatthe second conductive film is a transparent conductive film or aconductive film having reflectivity.

EMBODIMENT MODE OF THE INVENTION

The mode of carrying out the invention will be described below.

FIG. 1 is an example of a plan view of an active matrix substrate of thepresent invention, and here, for simplification, one pixel structureamong a plurality of pixels arranged in matrix form is shown. FIGS. 2and 3 are views showing a fabricating process.

As shown in FIG. 1, this active matrix substrate includes a plurality ofgate wiring lines arranged in parallel with each other, and a pluralityof source wiring lines perpendicular to the respective gate wiringlines.

A pixel electrode 127 comprising a transparent conductive film isdisposed at a region surrounded by the gate wiring lines and the sourcewiring lines. Besides, a transparent conductive film 128 overlaps withthe source wiring line so as not to overlap with the pixel electrode127.

Further, a capacitance wiring line 103 is disposed below the pixelelectrode 127, between adjacent two gate wiring lines, and in parallelwith the gate wiring line 102. This capacitance wiring line 103 isprovided for every pixel, and forms a storage capacitor with aninsulating film 111 shown in FIG. 2(B) as a dielectric.

Besides, a TFT as a switching element is provided in the vicinity of anintersection of the gate wiring line 102 and the source wiring line 125.This TFT is a reversed stagger type (or bottom gate type) TFT includinga channel formation region comprising a semiconductor film having anamorphous structure (hereinafter referred to as an amorphoussemiconductor film).

Besides, in this TFT, a gate electrode (formed integrally with the gatewiring line 102), a gate insulating film, an a-Si film, a source regionand a drain region comprising an n⁺a-Si film, a source electrode (formedintegrally with the source wiring line 125), and an electrode 126(hereinafter also referred to as a drain electrode) are sequentiallyformed to be laminated on an insulating substrate.

Besides, the gate insulating film does not exist over the gate wiringline in a region where the gate wiring line does not overlap with thea-Si film.

Thus, the pixel electrode 127 overlapping with the electrode 126 isformed so as not to overlap with the gate wiring line.

Besides, at the intersection of the gate wiring line and the sourcewiring line, the transparent conductive film at the end portion of thesource wiring line is removed so as to prevent shorting. Besides, theend of an electrode 117 is removed so as to prevent shorting between thecapacitance wiring line and the pixel electrode.

Besides, under the source wiring line (including the source electrode)and the drain electrode 126, the gate insulating film, the a-Si film,and the n⁺a-Si film are sequentially formed to be laminated on theinsulating substrate.

Besides, the a-Si film in a region between a region that contacts withthe source region and a region that contacts with the drain region, isthin as compared with that in the other regions. The film is thin since,when the n⁺a-Si film was separated by etching to form the source regionand the drain region, a part of the a-Si film was removed. Besides, bythis etching, an end surface of the pixel electrode, an end surface ofthe drain electrode, and an end surface of the drain region arecoincident with each other.

Besides, similarly, an end surface of the transparent conductive filmcovering the source electrode, an end surface of the source region, andan end surface of the source wiring line are coincident with each other.

The present invention made of the foregoing structure will be describedin more detail with embodiments shown below.

[Embodiments]

[Embodiment 1]

An embodiment of the invention are explained using FIGS. 1 to 6 and 9.The present embodiment shows a method of manufacturing a liquid crystaldisplay device, and a detailed explanation of a method of forming a TFTof a pixel portion on a substrate by a reversed stagger type TFT, andmanufacturing a storage capacitor connected to the TFT, is made inaccordance with the processes used. Further, a manufacturing process foran input terminal section, formed in an edge portion of the substrate,and for electrically connecting to wirings of circuits formed on othersubstrates, is shown at the same time in the same figures.

In FIG. 2(A), a glass substrate, comprising such as barium borosilicateglass or aluminum borosilicate glass, typically Corning Corp. #7059 or#1737, can be used as a substrate 100 having translucency. In addition,a translucent substrate such as a quartz substrate or a plasticsubstrate can also be used.

Next, after forming a conductive layer on the entire surface of thesubstrate, a first photolithography process is performed, a resist maskis formed, unnecessary portions are removed by etching, and wirings andelectrodes (the gate wiring 102 including a gate electrode, a capacitorwiring 103 and a terminal 101) are formed. Etching is performed at thistime to form a tapered portion in at least an edge portion of the gateelectrode 102. A top view of this stage is shown in FIG. 4.

It is preferable to form the gate wiring 102 including the gateelectrode, the capacitor wiring 103, and the terminal 101 of theterminal portion from a low resistivity conductive material such asaluminum (Al) or the like, but simple Al has problems such as inferiorheat resistance and easy to be corroded, and therefore it is combinedwith a heat resistant conductive material. One element selected from thegroup consisting of titanium (Ti), tantalum (Ta), tungsten (W),molybdenum (Mo), chromium (Cr), Neodymium (Nd), or an alloy comprisingthe above elements, or an alloy film of a combination of the aboveelement, or a nitrated compound comprising the above element is formedas the heat resistant conductive material. Furthermore, forming incombination with a heat resistant conductive material such as Ti, Si,Cr, or Nd, it is preferable because of improved flatness. Further, onlysuch heat resistant conductive film may also be formed, for example, incombination with Mo and W.

In realizing the liquid crystal display device, it is preferable to formthe gate electrode and the gate wiring by a combination of a heatresistant conductive material and a low resistivity conductive material.An appropriate combination in this case is explained.

Provided that the screen size is on the order of, or less than, 5 inchdiagonal type, a two layer structure of a lamination of a conductivelayer (A) comprising a nitride compound of a heat resistant conductivematerial, and a conductive layer (B) comprising a heat resistantconductive material is used. The conductive layer (B) may comprise anelement selected from the group consisting of Al, Ta, Ti, W, Nd, and Cr,or from an alloy of the above elements, or from an alloy film of acombination of the above elements, and the conductive layer (A)comprises a film such as a tantalum nitride (TaN) film, a tungstennitride (WN) film, or a titanium nitride (TiN) film. For example, it ispreferable to use a double layer structure of a lamination of Cr as theconductive layer (A) and Al containing Nd as the conductive layer (B).The conductive layer (A) is given a thickness of 10 to 100 nm(preferably between 20 and 50 nm), and the conductive layer (B) is madewith a thickness of 200 to 400 nm (preferably between 250 and 350 nm)

On the other hand, in order to be applied to a large screen, it ispreferable to use a three layer structure of a lamination of aconductive layer (A) comprising a heat resistant conductive material, aconductive layer (B) comprising a low resistivity conductive material,and a conductive layer (C) comprising a heat resistant conductivematerial. The conductive layer (B) comprising the low resistivityconductive material comprises a material comprising aluminum (Al), andin addition to pure Al, Al containing between 0.01 and 5 atomic % of anelement such as scandium (Sc), Ti, Nd, or silicon (Si), etc. is used.The conductive layer (C) is effective in preventing generation ofhillocks in the Al of the conductive layer (B). The conductive layer (A)is given a thickness of 10 to 100 nm (preferably between 20 and 50 nm),the conductive layer (B) has 200 to 400 nm thick (preferable between 250and 350 nm), and the conductive layer (C) is from 10 to 100 nm thick(preferably between 20 and 50 nm) In the present embodiment, theconductive layer (A) comprises a Ti film with a thickness of 50 nm, madeby sputtering with a Ti target, the conductive layer (B) comprises an Alfilm with a thickness of 200 nm, made by sputtering with an Al target,and the conductive layer (C) is a 50 nm thick Ti film, made bysputtering with a Ti target.

An insulating film 104 is formed next on the entire surface. Theinsulating film 104 is formed using sputtering, and has a film thicknessof 50 to 200 nm.

For example, a silicon nitride film is used as the insulating film 104,and formed to a thickness of 150 nm. Of course, the gate insulating filmis not limited to this type of silicon nitride film, and anotherinsulating film such as a silicon oxide film, a silicon oxynitride film,or a tantalum oxide film may also be used, and the gate insulating filmmay comprise a single layer or a lamination structure comprising thesematerials. For example, a lamination structure having a silicon nitridefilm as a lower layer and a silicon oxide film as an upper layer may beused.

Next, an amorphous semiconductor film 105 is formed with a thickness of50 to 200 nm (preferably between 100 and 150 nm) on the insulating film104 over the entire surface by using a known method such as plasma CVDor sputtering (not shown in the figure). Typically, an amorphous silicon(a-Si) film is formed with a thickness of 100 nm by sputtering using asilicon target. In addition, it is also possible to apply amicrocrystalline semiconductor film, or a compound semiconductor filmhaving an amorphous structure, such as an amorphous silicon germaniumfilm.

An amorphous semiconductor film 106 containing an impurity elementimparting n-type is formed next with a thickness of 20 to 80 nm as asemiconductor film 106 which contains an impurity element imparting oneconductivity type. The amorphous semiconductor film 106 containing animpurity element imparting n-type is formed on the entire surface by aknown method such as plasma CVD or sputtering. Typically it isappropriate to form an n⁺a-Si:H film, and it is deposited by using asilicon target added with phosphorus (P). Alternatively, film depositionmay be performed by sputtering using a silicon target in an atmospherecontaining phosphorous. In addition, the amorphous semiconductor film106 containing an impurity element imparting n-type may also comprise ahydrogenated microcrystalline silicon film (μc-Si:H).

Next, a conductive metal film 107 is formed by sputtering or vacuumevaporation. Provided that ohmic contact with the n⁺a-Si film 106 can bemade, there are no particular limitation on the material of theconductive metal film 107, and an element selected from the groupconsisting of Al, Cr, Ta, and Ti, or an alloy comprising the aboveelements, and an alloy film of a combination of the above elements orthe like can be given. Note however that it is necessary to choose amaterial for the conductive metal film 107 which has a sufficientselective ratio with respect to the terminal and the gate wiring in thelater etching process. In the present embodiment, sputtering is used anda Cr film having 300 to 600 thickness is formed as the metal film 107.(FIG. 2(A))

The insulating film 104, the amorphous semiconductor film 105, thesemiconductor film 106 containing an impurity element which imparts oneconductivity type, and the conductive metal film 107 are allmanufactured by a known method, and can be manufactured by plasma CVD orsputtering. The films are formed in succession by sputtering, andsuitably changing the target or the sputtering gas in the presentembodiment. The same reaction chamber, or a plurality of reactionchambers, in the sputtering apparatus is used at this time, and it ispreferable to laminate these films in succession without exposure to theatmosphere. By thus not exposing the films to the atmosphere, the mixingin of impurities can be prevented.

Next, a second photolithography process is performed, resist masks 108and 109 are formed, and by removing unnecessary portions by etching,insulating films 110 and 111, a wiring and an electrode (source wiring)are formed. Wet etching or dry etching is used as the etching process atthis time. The insulating film 104, the amorphous semiconductor film105, the semiconductor film 106 containing an impurity element impartingone conductivity type and the conductive metal film 107 are etched inthe second photolithograpy process, and an insulating film 110, anamorphous semiconductor film 112, a semiconductor film containing animpurity element imparting one conductivity type 114 and a conductivemetal film 116 are formed in the pixel TFT portion. Accordingly the edgesurface of the films approximately coincide. Further in the capacitorportion an insulating film 111, an amorphous semiconductor film 113, asemiconductor film 115 containing an impurity element imparting oneconductivity type and a conductive metal film 117 are formed. Similarly,the edge surface of these films coincide.

Further, in the above second photolithography process, the films areetched away leaving only the terminal 101 in the terminal portion. Theinsulating film on the gate wiring is also removed by leaving onlyintersecting portion with other wirings. Accordingly it is necessary toselect a material for the terminal 101 and gate wiring that hassufficient selective ratio with respect to that of the insulating film,and it is further necessary to select a material which has a sufficientselective ratio for the materials of the terminal with respect to thatof the conductive metal film. That is, it is necessary to choosedifferent materials for the terminal and the gate wiring from that ofthe conductive metal film. In the present embodiment, the metal film 107is etched by dry etching using a mixed gas of Cl₂ and O₂, and then thesemiconductor film 106 containing an impurity element imparting oneconductivity type, the amorphous semiconductor film 105 and theinsulating film 104 are selectively removed by changing the reaction gasto a mixed gas of CF₄ and O₂. (FIG. 2(B))

Next, after removing the resist mask 108, a transparent conductive film118 is deposited over the entire surface. (FIG. 2(C)) A top view in thisstate is shown in FIG. 5. Note however, for simplification, thetransparent conductive film 118 deposited over the entire surface is notshown in FIG. 5.

The transparent conductive film 118 comprises a material such as indiumoxide (In₂O₃) or indium oxide tin oxide alloy (In₂O₃—SnO₂, abbreviatedas ITO) using a method such as sputtering or vacuum evaporation. Theetching process for this type of material is performed using a solutionof hydrochloric acid type. However, a residue is easily generated,particularly in ITO etching, and therefore an indium oxide zinc oxidealloy (In₂O₃ —ZnO) may be used in order to improve the etchingworkability. The indium oxide zinc oxide alloy has superior surfacesmoothing characteristics, and has superior thermal stability comparedto ITO, and therefore even if the electrode 116 comprises an Al film, acorrosion reaction can be prevented. Similarly, zinc oxide (ZnO) is alsoa suitable material, and in addition, in order to increase thetransmittivity of visible light and increase the conductivity, amaterial such as zinc oxide in which gallium (Ga) is added (ZnO:Ga) canbe used.

Resist masks 119, 120 and 121 are formed next by a thirdphotolithography process. Unnecessary portions are then removed byetching, forming an amorphous semiconductor film 122, a source region123, a drain region 124, the source electrode 125, the drain electrode126, and the pixel electrode 127. (FIG. 2(D))

The third photolithography process patterns the transparent conductivefilm 118, and at the same time removes a part of the conductive metalfilm 116, the n⁺a-Si film 114 and the amorphous semiconductor film 112by etching, forming an opening. In the present embodiment, the pixelelectrode comprising ITO is selectively removed first by wet etchingusing a mixed solution of nitric acid and hydrochloric acid, or a ferricchloride solution, and after removing the conductive metal film 116 bywet etching, a part of the n⁺a-Si film 114 and the amorphoussemiconductor film 112 are etched by dry etching Note that wet etchingand dry etching are used in the present embodiment, but the operator mayperform only dry etching by suitably selecting the reaction gas, and theoperator may perform only wet etching by suitably selecting the reactionsolution.

Further, the lower portion of the opening reaches the amorphoussemiconductor film, and the amorphous semiconductor film 114 is formedhaving a concave portion. The conductive metal film 116 is separatedinto the source wiring 125 and the drain electrode 126 by the opening,and the n⁺a-Si:H film 114 is separated into the source region 123 andthe drain region 124. Furthermore, the transparent conductive film 128contacting the source electrode 125 covers the source wiring, and duringsubsequent manufacturing processes, especially during a rubbing process,fulfills a role of preventing static electricity from developing. Anexample of forming the transparent conductive film 128 on the sourcewiring is shown in the present embodiment, but the transparentconductive film 128 may also be removed during the above etching of theITO film. In addition, a circuit for protecting from static electricitymay be formed by utilizing the above ITO film, in the etching of the ITOfilm.

Further, though not shown in the figure, it is necessary that the gatewiring have selective ratio with the amorphous semiconductor film andthe metal film 116 since the transparent conductive film formed on thegate wiring is selectively removed by the above third photolithographyprocess. Note however the transparent conductive film is partially leftin the gate wiring terminal portion.

Resist masks 119 to 121 are next removed. The cross sectional view ofthis state is shown in FIG. 3(A). Note that FIG. 1 is a top view of onepixel and the cross sections along the A-A′ line and the B-B′ linecorrespond to FIG. 3(A) respectively.

Furthermore, FIG. 9(A) shows top views of a gate wiring terminal portion501 and a source wiring terminal portion 502 in this state. Note thatthe same symbols are used for area corresponding to those of FIG. 1 toFIG. 3. Further, FIG. 9(B) corresponds to a cross-sectional view takenalong the lines E-E′ and F-F′ in FIG. 9(A). Reference numeral 503 inFIG. 9(A) comprising a transparent conductive film denotes a connectingelectrode which functions as an input terminal. In addition, in FIG.9(B) reference numeral 504 denotes an insulating film (extended from110), reference numeral 505 denotes an amorphous semiconductor film(extended from 122), and reference numeral 506 denotes an n⁺a-Si film(extended from 123).

Note that a storage capacitor is formed in the capacitor portion betweenthe capacitor wiring 103 and the metal film 117 (or n⁺a-Si film 115 orsemiconductor film) with the insulating film 111 as a dielectric.

By thus using three photomasks and performing three photolithographyprocesses, the pixel TFT portion having the reversed stagger typen-channel type TFT 201 and the storage capacitor 202 can be completed.By placing these in matrix form corresponding to each pixel and thuscomposing the pixel portion, one substrate can be made in order tomanufacture an active matrix liquid crystal display device. Forconvenience, this type of substrate is referred to as an active matrixsubstrate throughout this specification.

An alignment film 130 is selectively formed next in only the pixelportion of the active matrix substrate. Screen printing may be used as amethod of selectively forming the alignment film 130, and a method ofremoval in which a resist mask is formed using a shadow mask afterapplication of the alignment film may also be used. Normally, apolyimide resin is often used in the alignment film of the liquidcrystal display element.

Next, a rubbing process is then performed on the alignment film 130,orienting the liquid crystal elements so as to possess a certain fixedpre-tilt angle.

The active matrix substrate, and an opposing substrate 133 on which anopposing electrode 132, and an alignment film 131 are formed are nextjoined together by a sealant while maintaining a gap between thesubstrates using spacers, after which a liquid crystal material 134 isinjected into the space between the active matrix substrate and theopposing substrate. A known material may be applied for the liquidcrystal material 134, and a TN liquid crystal is typically used. Afterinjecting the liquid crystal material, the injecting entrance is sealedby a resin material.

Next, a flexible printed circuit (FPC) is connected to the terminal 101of the terminal portion. The FPC comprises a copper wiring 137 on anorganic resin film 138 such as polyimide, and is connected to the inputterminal 129 comprising a transparent conductive film (corresponding toreference numeral 503 of FIG. 9) by an anisotropic conductive adhesive.The anisotropic conductive adhesive comprises an adhesive 135 andparticles 136, with a diameter of several tens to several hundred of μmand having a conductive surface plated by a material such as gold, whichare mixed therein. The particles 136 form an electrical connection inthis portion by connecting the input terminal 129 and the copper wiring137. In addition, in order to increase the mechanical strength of thisregion, a resin layer 139 is formed. (FIG. 3(B))

FIG. 6 is a diagram explaining the placement of the pixel portion andthe terminal portion of the active matrix substrate. A pixel portion 211is formed on a substrate 210, gate wirings 208 and source wirings 207are formed intersecting on the pixel portion, and the n-channel TFT 201connected to this is formed corresponding to each pixel. The pixelelectrode 127 and a storage capacitor 202 are connected to the drainside of the n-channel TFT 201, and the other terminal of the storagecapacitor 202 is connected to a capacitor wiring 209. The structure ofthe n-channel TFT 201 and the storage capacitor 202 is the same as thatof the n-channel TFT 201 and the storage capacitor 202 shown by FIG.3(A).

An input terminal portion 205 for inputting a scanning signal is formedin one edge portion of the substrate, and is connected to a gate wiring208 by a connection wiring 206. Further, an input terminal portion 203for inputting an image signal is formed in the other edge portion, andis connected to a source wiring 207 by a connection wiring 204. Aplurality of the gate wiring 208, the source wiring 207, and thecapacitor wiring 209 are formed in accordance with the pixel density.The number of the wirings is as stated above. Furthermore, an inputterminal portion 212 for inputting an image signal and a connectionwiring 213 may be formed, and may be connected to the source wiringalternately with the input terminal portion 203. An arbitrary number ofthe input terminal portions 203, 205, and 212 are formed, which may besuitably determined by the operator.

[Embodiment 2]

FIG. 7 is an example of a method of mounting a liquid crystal displaydevice. The liquid crystal display device has an input terminal portion302 formed in an edge portion of a substrate 301 on which TFTs areformed, and as shown by embodiment 1, this is formed by a terminal 303comprising the same material as the gate wiring. An opposing substrate304 is joined to the substrate 301 by a sealant 305 encapsulatingspacers 306, and in addition, polarizing plates 307 and 308 are formed.This is then fixed to a casing 321 by spacers 322.

Note that the TFT obtained in Embodiment 1 having an active layer formedby an amorphous semiconductor film has a low electric field effectmobility, and only approximately 1 cm²/Vsec is obtained. Therefore, adriver circuit for performing image display is formed by a LSI chip, andmounted by a TAB (tape automated bonding) method or by a COG (chip onglass) method. In the present embodiment, an example is shown of formingthe driver circuit in a LSI chip 313, and mounting by using the TABmethod. A flexible printed circuit (FPC) is used, and the FPC is formedby a copper wiring 310 on an organic resin film 309, such as polyimide,and is connected to the input terminal 302 by an anisotropic conductiveadhesive. The input terminal is a transparent conductive film formed onand contacting the wiring 303. The anisotropic conductive adhesive isstructured by an adhesive 311 and particles 312, with a diameter ofseveral tens to several hundred of μm and having a conductive surfaceplated by a material such as gold, which are mixed therein. Theparticles 312 form an electrical connection in this portion byconnecting the input terminal 302 and the copper wiring 310. Inaddition, in order to increase the mechanical strength of this region, aresin layer 318 is formed.

The LSI chip 313 is connected to the copper wiring 310 by a bump 314,and is sealed by a resin material 315. The copper wiring 310 is thenconnected to a printed substrate 317 on which other circuits such as asignal processing circuit, an amplifying circuit, and a power supplycircuit are formed, through a connecting terminal 316. A light source319 and a light conductor 320 are formed on the opposing substrate 304and used as a back light in the transmitting liquid crystal displaydevice.

[Embodiment 3]

In the present embodiment, an example of forming a protecting film isshown in FIG. 6. Note that the present embodiment is identical toEmbodiment 1 till the state of FIG. 2(D), and therefore only points ofdifference are explained. Further, the same symbols are used forlocations corresponding to those in FIG. 2(D).

After first forming through the state of FIG. 2(D) in accordance withEmbodiment 1, a thin inorganic insulating film is formed on the entiresurface. An inorganic insulating film formed as the thin inorganicinsulating film using a silicon oxide film, a silicon nitride film, asilicon oxynitride film, or a tantalum oxide film, and a single layer ora lamination structure comprising these materials may be formed.

A forth photolithography process is performed next, forming a resistmask, and unnecessary portions are removed by etching, forming aninsulating film 402 in the pixel TFT portion, and an inorganicinsulating film 401 in the terminal portion. These inorganic insulatingfilms 401 and 402 function as passivation films. Further, the thininorganic insulating film 401 is removed in the terminal portion by thefourth photolithography process, exposing the terminal 101 of theterminal portion.

The reversed stagger type n-channel type TFT and the storage capacitor,protected by the inorganic insulating film, can thus be completed in thepresent embodiment by performing the photolithography process using fourphotomasks four times in total. Thus the pixel portion is structured byarranging these into a matrix state corresponding to each pixel, and onesubstrate for manufacturing the active matrix liquid crystal displaydevice can be made.

Note that it is possible to freely combine the constitution of thepresent embodiment with that of Embodiment 1 or Embodiment 2.

[Embodiment 4]

Although Embodiment 1 show an example of laminating an insulating film,an amorphous semiconductor film, an amorphous semiconductor filmcontaining an impurity element which imparts n-type conductivity, and ametal film by sputtering, but the present embodiment shows an example ofusing plasma CVD to form the films.

The insulating film, the amorphous semiconductor film, and the amorphoussemiconductor film containing an impurity element which imparts n-typeconductivity are formed by plasma CVD in the present embodiment.

In the present embodiment, a silicon oxynitride film is used as theinsulating film, and formed with a thickness of 150 nm by plasma CVD.Plasma CVD may be performed at this point with a power supply frequencyof 13 to 70 MHz, preferably between 27 and 60 MHz. By using a powersupply frequency of 27 to 60 MHz, a dense insulating film can be formed,and the voltage resistance can be increased as a gate insulating film.Further, a silicon oxynitride film manufactured by adding O₂ to SiH₄ andN₂O has a reduction in fixed electric charge density in the film, andtherefore is a material which is preferable for this use. Of course, thegate insulating film is not limited to this type of silicon oxynitridefilm, and a single layer or a lamination structure using otherinsulating films such as s silicon oxide film, a silicon nitride film,or a tantalum oxide film may be formed. Further, a lamination structureof a silicon nitride film in a lower layer, and a silicon oxide film inan upper layer may be used.

For example, when using a silicon oxide film, it can be formed by plasmaCVD using a mixture of tetraethyl orthosilicate (TEOS) and O₂, with thereaction pressure set to 40 Pa, a substrate temperature of 250 to 350°C., and discharge at a high frequency (13.56 MHz) power density of 0.5to 0.8 W/cm². Good characteristics as the gate insulating film can beobtained for the silicon oxide film thus formed by a subsequent thermalanneal at 300 to 400° C.

Typically, a hydrogenated amorphous silicon (a-Si:H) film is formed witha thickness of 100 nm by plasma CVD as the amorphous semiconductor film.At this point, plasma CVD may be performed with a power supply frequencyof 13 to 70 MHz, preferably between 27 and 60 MHz, in the plasma CVDapparatus. By using a power frequency of 27 to 60 MHz, it becomespossible to increase the film deposition speed, and the deposited filmis preferable because it becomes an a-Si film having a low defectdensity. In addition, it is also possible to apply a microcrystallinesemiconductor film and a compound semiconductor film having an amorphousstructure, such as an amorphous silicon germanium film, as the amorphoussemiconductor film.

Further, if 100 to 100 k Hz pulse modulation discharge is performed inthe plasma CVD film deposition of the insulating film and the amorphoussemiconductor film, then particle generation due to the plasma CVD gasphase reaction can be prevented, and pinhole generation in the formedfilm can also be prevented, and therefore is preferable.

Further, in the present embodiment, an amorphous semiconductor filmcontaining an impurity element which imparts n-type conductivity isformed with a thickness of 20 to 80 nm as a semiconductor filmcontaining a single conductivity type impurity element. For example, ana-Si:H film having n-type may be formed, and in order to do so,phosphine (PH₃) is added at a 0.1 to 5% concentration to silane (SiH₄).Alternatively, a hydrogenated microcrystalline silicon film (μc-Si:H)may also be used as a substitute for the amorphous semiconductor film106, containing an impurity element which imparts n-type conductivity.

These films can be formed in succession by appropriately changing thereaction gas. Further, these films can be laminated successively withoutexposure to the atmosphere at this time by using the same reactionchamber or a plurality of reaction chambers in the plasma CVD apparatus.By thus depositing successively these films without exposing the filmsto the atmosphere, the mixing in of impurities into the first amorphoussemiconductor film can be prevented.

Note that it is possible to combine the present embodiment withEmbodiment 2.

[Embodiment 5]

Examples are shown in Embodiment 1 and Embodiment 4 of laminating aninsulating film, an amorphous semiconductor film, an n⁺a-Si film, and ametal film, in order and in succession. An example of an apparatushaving a plurality of chambers, and used for cases of performing thistype of successive film deposition is shown in FIG. 10.

An outline of an apparatus (successive film deposition system), shown bythe present embodiment, is shown in FIG. 10 as seen from above.Reference numerals 10 to 15 in FIG. 10 denote chambers having airtightcharacteristics. A vacuum evacuation pump and an inert gas introductionsystem are arranged in each of the chambers.

The chambers denoted by reference numerals 10 and 15 are load-lockchambers for bringing sample (processing substrate) 30 into the system.The chamber denoted by reference numeral 11 is a first chamber fordeposition of the insulating film 104. The chamber denoted by referencenumeral 12 is a second chamber for deposition of the amorphoussemiconductor film 105. The chamber denoted by reference numeral 13 is athird chamber for deposition of the amorphous semiconductor film 106which imparts n-type conductivity. The chamber denoted by referencenumeral 14 is a fourth chamber for deposition of the metal film 107.Further, reference numeral 20 denotes a common chamber for the sample,arranged in common with respect to each chamber.

An example of operation is shown below.

After pulling an initial high vacuum state in all of the chambers atfirst, a purge state (normal pressure) is made by using an inert gas,nitrogen here. Furthermore, all gate valves 22 to 27 are closed.

First, a cassette 28 loaded with a multiple number of processingsubstrate is placed into the load-lock chamber 10. After the cassette isplaced inside, a door of the load-lock chamber (not shown in the figure)is closed. In this state, the gate valve 22 is opened and one of theprocessing substrate 30 is removed from the cassette, and is taken outto the common chamber 20 by a robot arm 21. Position alignment isperformed in the common chamber at this time. Note that a substrate onwhich the wirings 101, 102, and 103 are formed, in accordance withEmbodiment 1, is used for the substrate 30.

The gate valve 22 is then closed, and a gate valve 23 is opened next.The processing substrate 30 is then moved into the first chamber 11.Film deposition processing is performed within the first chamber at atemperature of 150 to 300° C., and the insulating film 104 is obtained.Note that a film such as a silicon nitride film, a silicon oxide film, asilicon oxynitride film, or a lamination film of these films, can beused as the insulating film. A single layer silicon nitride film isemployed in the present embodiment, but a two-layer, three-layer, orhigher layer lamination structure film may also be used. Note that achamber capable of plasma CVD is used here, but a chamber which iscapable of sputtering by utilizing a target may also be used.

After completing the deposition of the insulating film, the processingsubstrate is pulled out into the common chamber by the robot arm, and isthen transported to the second chamber 12. Film deposition is performedwithin the second chamber at a temperature of 150 to 300° C., similar tothat of the first chamber, and the amorphous semiconductor film 105 isobtained by plasma CVD. Note that a film such as a microcrystallinesemiconductor film, an amorphous germanium film, an amorphous silicongermanium film, or a lamination film of these films, etc., can be usedas the amorphous semiconductor film. Further, a heat treatment processfor reducing the concentration of hydrogen may be omitted with aformation temperature of 350 to 500° C. for the amorphous semiconductorfilm. Note that a chamber capable of plasma CVD is used here, but achamber which is capable of sputtering by use of a target may also beused.

After completing deposition of the amorphous semiconductor film, theprocessing substrate is pulled out into the common chamber and thentransported to the third chamber 13. Film deposition process isperformed within the third chamber at a temperature of 150 to 300° C.,similar to that of the second chamber, and the amorphous semiconductorfilm 106, containing an impurity element which imparts n-typeconductivity (P or As), is obtained by plasma CVD. Note that a chambercapable of plasma CVD is used here, but a chamber which is capable ofsputtering by use of a target may also be used.

After completing deposition of the amorphous semiconductor filmcontaining an impurity element which imparts n-type conductivity, theprocessing substrate is pulled out into the common chamber, and then istransported to the fourth chamber 14. The metal film 107 is obtainedwithin the fourth chamber by sputtering using a metallic target.

The processed substrate, on which four layers have thus been formed insuccession, is then transported to the load-lock chamber 15 by the robotarm, and is contained in a cassette 29.

Note that the apparatus shown in FIG. 10 is only one example. Further,it is possible to freely combine the present embodiment with any one ofEmbodiments 1 to 4.

[Embodiment 6]

In Embodiment 5, an example of successive lamination using a pluralityof chambers is shown, but in the present embodiment, a method ofsuccessive lamination within one chamber maintained at high vacuum usingthe apparatus shown in FIG. 11 is employed.

The apparatus system shown in FIG. 11 is used in the present embodiment.In FIG. 11, reference numeral 40 denotes a processing substrate,reference numeral 50 denotes a common chamber, 44 and 46 denoteload-lock chambers, 45 denotes a chamber, and reference numerals 42 and43 denote cassettes. In order to prevent contamination developing duringtransport of the substrate, lamination is performed in the same chamberin the present embodiment.

It is possible to freely combine the present embodiment with any one ofEmbodiments 1 to 4.

Note that, when it is applied to Embodiment 1, a plurality of targetsare prepared in the chamber 45, and then the insulating film 104, theamorphous semiconductor film 105, the amorphous semiconductor film 106containing an impurity element which imparts n-type conductivity, andthe metal film 107 may be laminated by changing the reaction gas inorder.

Further, when applied to Embodiment 3, the insulating film 104, theamorphous semiconductor film 105, and the amorphous semiconductor film106 containing an impurity element which imparts n-type conductivity,may be laminated by changing the reaction gas in order.

[Embodiment 7]

In Embodiment 1, an example of forming the n⁺a-Si film by usingsputtering is shown, but in the present embodiment, an example offorming it by using plasma CVD is shown. Note that, except for themethod of forming the n⁺a-Si film, the present embodiment is identicalto Embodiment 1, and therefore only differing points are stated below.

If phosphine (PH₃) is added at a concentration of 0.1 to 5% with respectto silane (SiH₄) as a reaction gas using plasma CVD, then the n⁺a-Sifilm can be obtained.

[Embodiment 8]

In Embodiment 7, an example of forming the n⁺a-Si film by using plasmaCVD is shown, and in the present embodiment, an example of using amicrocrystalline semiconductor film containing an impurity element whichimparts n-type conductivity y is shown.

By setting the deposition temperature from 80 to 300° C., preferablybetween 140 and 200° C., taking a gas mixture of silane diluted byhydrogen (SiH₄:H₂=1:10 to 100) and phosphine (PH₃) as the reaction gas,setting the gas pressure from 0.1 to 10 Torr, and setting the dischargepower from 10 to 300 mW/cm², a microcrystalline silicon film can beobtained. Further phosphorous may be added by plasma doping after filmdeposition of this microcrystalline silicon film.

[Embodiment 9]

FIG. 12 is a diagram which schematically shows a state of constructingan liquid crystal display device by using the COG method. A pixel region803, an external input-output terminal 804, and a connection wiring 805are formed on a first substrate. Regions surrounded by dotted linesdenote a region 801 for attaching a scanning line side IC chip, and aregion 802 for attaching a data line side IC chip. An opposing electrode809 is formed on a second substrate 808, and this is joined to the firstsubstrate 800 by using a sealing material 810. A liquid crystal layer811 is formed inside the sealing material 810 by injecting a liquidcrystal. The first substrate and the second substrate are joined with apredetermined gap, and this is set from 3 to 8 μm for a nematic liquidcrystal, and from 1 to 4 μm for a smectic liquid crystal.

IC chips 806 and 807 have circuit structures which differ between thedata line side and the scanning line side. The IC chips are mounted onthe first substrate. An FPC (flexible printed circuit) 812 is attachedto the external input-output terminal 804 in order to input power supplyand control signals from the outside. In order to increase the adhesionstrength of the FPC 812, a reinforcement 813 may be formed. The liquidcrystal display device can thus be completed. If an electricalinspection is performed before mounting the IC chips on the firstsubstrate, then the final process yield of the liquid crystal displaydevice can be improved, and the reliability can be increased.

Further, a method such as a method of connection using an anisotropicconductive material or a wire bonding method, can be employed as themethod of mounting the IC chips on the first substrate. FIG. 13 showsexamples of such. FIG. 13(A) shows an example in which an IC chip 908 ismounted on a first substrate 901 using an anisotropic conductivematerial. A pixel region 902, a lead wire 906, a connection wiring andan input-output terminal 907 are formed on the first substrate 901. Asecond substrate is bonded to the first substrate 901 by using a sealingmaterial 904, and a liquid crystal layer 905 is formed therebetween.

Further, an FPC 912 is bonded to one edge of the connection wiring andthe input-output terminal 907 by using an anisotropic conductivematerial. The anisotropic conductive material comprises a resin 915 andconductive particles 914 having a diameter of several tens to severalhundred of μm and plated by a material such as Au, and the connectionwiring 913 formed with the FPC 912, and the connection wiring and theinput-output terminal 907 are electrically connected by the conductiveparticles 914. The IC chip 908 is also similarly bonded to the firstsubstrate by an anisotropic conductive material. An input-outputterminal 909 provided with the IC chip 908 and the lead wire 906 or aconnection wiring and the input-output terminal 907 are electricallyconnected by conductive particles 910 mixed into a resin 911.

Furthermore, as shown by FIG. 13(B), the IC chip may be fixed to thefirst substrate by an adhesive material 916, and an input-outputterminal of a stick driver and a lead wire or a connection wiring may beconnected by an Au wire 917. Then, this is all sealed by a resin 918.

The method of mounting the IC chip is not limited to the method based onFIGS. 12 and 13, and it is also possible to use a known method notexplained here, such as a COG method, a wire bonding method or a TABmethod.

It is possible to freely combine the present embodiment with Embodiment1.

[Embodiment 10]

In Embodiment 1, a method of manufacturing an active matrix substratecorresponding to a transmission type liquid crystal display device isshown, but in the present embodiment, an example of application to areflection type liquid crystal display device is shown, using FIG. 14.

First, in the same way as the embodiment 1, steps up to the step shownin FIG. 2(B) are carried out. Then, an interlayer insulating filmcomprising an organic resin film is formed. Next, a roughening processof the interlayer insulating film is carried out to form an interlayerinsulating film 601 having a roughened portion. As the rougheningprocess, a method of applying an organic resin film containing fibers orspacers may be used, a method of formation by partially etching anorganic resin film by using a mask may be used, or a method of formationby heating to perform reflow after a photosensitive resin is etched byusing a mask to make a cylindrical shape, may be used.

Next, contact holes reaching a source wiring line and a drain electrodeare formed in the interlayer insulating film 601 by a thirdphotolithography step. Besides, in order to form a storage capacitor bythe same step, at the same time that the contact hole reaching theelectrode is formed, the interlayer insulating film on a terminalportion is removed.

Next, a conductive film (Al, Ag, etc.) having reflectivity is formed.

Then, a resist mask pattern is formed by a fourth photolithography step,and a pixel electrode 602 made of the conductive film having thereflectivity is formed by etching The pixel electrode 602 formed in thisway has a roughened portion, can disperse light, and can preventformation of a mirror surface. At the same time, a lead wiring line 603reaching a source electrode is formed.

Since subsequent steps are the same as the embodiment 1, they areomitted. In this way, an active matrix substrate corresponding to areflection type liquid crystal display device can be fabricated throughfour photolithography steps using four photomasks.

Besides, the present embodiment can be combined with the embodiment 2 orthe embodiment 3.

[Embodiment 11]

CMOS circuits and pixel portion formed by implementing the presentinvention can be used in various electro-optical devices (such as anactive matrix liquid crystal display device and an active matrix ECdisplay device). Namely, the present invention can be implemented in allelectronic appliance in which these electro-optical devices are builtinto a display portion.

The following can be given as such electronic appliance: a video camera,a digital camera, a projector (rear type or front type), a head-mounteddisplay (goggle type display), a car navigation system, a car stereo, apersonal computer, and a portable information terminal (such as a mobilecomputer, a portable telephone or an electronic book). Examples of theseare shown in FIGS. 15, 16 and 17.

FIG. 15(A) is a personal computer, and it includes a main body 2001, animage input portion 2002, a display portion 2003, and a keyboard 2004,etc. The present invention can be applied to the image input portion2002, the display portion 2003 or other signal driver circuits.

FIG. 15(B) is a video camera, and it includes a main body 2101, adisplay portion 2102, an audio input portion 2103, operation switches2104, a battery 2105, and an image receiving portion 2106, etc. Thepresent invention can be applied to the display portion 2102 or othersignal driver circuits.

FIG. 15(C) is a mobile computer, and it includes a main body 2201, acamera portion 2202, an image receiving portion 2203, operation switches2204, and a display portion 2205, etc. The present invention can beapplied to the display portion 2205 or other signal driver circuits.

FIG. 15(D) is a goggle type display, and it includes a main body 2301, adisplay portion 2302, an arm portion 2303, etc. The present inventioncan be applied to the display portion 2302 or other signal drivercircuits.

FIG. 15(E) is a player that uses a recording medium on which a programis recorded (hereafter referred to as a recording medium), and theplayer includes a main body 2401, a display portion 2402, a speakerportion 2403, a recording medium 2404, and operation switches 2405, etc.Note that this player uses a recording medium such as a DVD (digitalversatile disk) or a CD, and the appreciation of music, the appreciationof film, game playing and the Internet can be performed. The presentinvention can be applied to the display portion 2402 or other signaldriver circuits.

FIG. 15(F) is a digital camera, and it includes a main body 2501, adisplay portion 2502, an eyepiece portion 2503, operation switches 2504,and an image receiving portion (not shown in the figure), etc. Thepresent invention can be applied to the display portion 2502 or othersignal driver circuits.

FIG. 16(A) is a front projector, and it includes a projection system2601, a screen 2602, etc. The present invention can be applied to aliquid crystal display device 2808 which constitutes a part of theprojection system 2601, or other signal driver circuits.

FIG. 16(B) is a rear projector, and it includes a main body 2701, aprojection system 2702, a mirror 2703, a screen 2704, etc. The presentinvention can be applied to a liquid crystal display device 2808 whichconstitutes a part of the projection system 2702 or other signal drivercircuits.

Note that FIG. 16(C) is a diagram showing an example of the structure ofprojection systems 2601 and 2702 of FIGS. 16(A) and 16(B). Theprojection systems 2601 and 2702 comprise an optical light source system2801, mirrors 2802 and 2804 to 2806, a dichroic mirror 2803, a prism2807, a liquid crystal display device 2808, phase differentiating plate2809 and a projection optical system 2810. The projection optical system2810 comprises an optical system including a projection lens. Thepresent Embodiment showed a three plate type, but it is not limited tothis structure, and it may be for instance a single plate type. Further,the operator may appropriately dispose an optical system such as anoptical lens, a film having light polarizing function, a film foradjusting phase difference and an IR film, in the optical path shown byan arrow in the FIG. 16(C).

FIG. 16(D) is a diagram showing an example of the structure of theoptical light source system 2801 of FIG. 16(C). In the presentembodiment the optical light source system 2801 comprises a reflector2811, a light source 2812, lens arrays 2813 and 2814, light polarizingconversion element 2815 and a condenser lens 2816. Note that the opticallight source system shown in FIG. 16(D) is merely an example and is notspecifically limited. For example, the operator may appropriatelydispose an optical system such as an optical lens, a film having lightpolarizing function, a film for adjusting phase difference and an IRfilm, etc., in the optical light source system.

Provided however, the projectors shown in FIG. 16 show a case of usingtransmission type electro-optical device and an application example ofreflection type electro-optical device is not shown in the figures.

FIG. 17(A) is a portable telephone, and it includes a main body 2901, anaudio output portion 2902, an audio input portion 2903, a displayportion 2904, operation switches 2905, and an antenna 2906, etc. Thepresent invention can be applied to the audio output portion 2902, theaudio input portion 2903, the display portion 2904 or other signaldriver circuits.

FIG. 17(B) is a portable book (electronic book), and it includes a mainbody 3001, display portions 3002 and 3003, a recording medium 3004,operation switches 3005, and an antenna 3006, etc. The present inventioncan be applied to the display portions 3002 and 3003 or other signaldriver circuits.

FIG. 17(C) is a display, and it includes a main body 3101, a supportstand 3102, and a display portion 3103, etc. The present invention canbe applied to the display portion 3103. The display of the presentinvention is advantageous for a large size screen in particular, and isadvantageous for a display equal to or greater than 10 inches(especially equal to or greater than 30 inches) in diagonal.

The applicable range of the present invention is thus extremely wide,and it is possible to apply the present invention to electronicappliance in all fields. Further, the electronic appliance of thepresent embodiment can be realized by using a constitution of anycombination of embodiments 1 to 10.

Effects of the Invention

With the present invention, a liquid crystal display device preparedwith a pixel TFT portion, having a reversed stagger type n-channel TFT,and a storage capacitor can be realized through three photolithographysteps using three photomasks.

Further, when forming a protecting film, a liquid crystal display deviceprepared with a pixel TFT portion, having a reversed stagger typen-channel TFT protected by an inorganic insulating film, and a storagecapacitor can be realized through four photolithography steps using fourphotomasks.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A view showing a top view of the present invention.

[FIGS. 2A-2D] Sectional views showing a fabricating process of anAM-LCD.

[FIGS. 3A and 3B] Sectional views showing the fabricating process of theAM-LCD.

[FIG. 4] A top view showing a fabricating process of an AM-LCD.

[FIG. 5] A top view showing the fabricating process of the AM-LCD.

[FIG. 6] A top view for explaining the arrangement of a pixel portionand an input terminal portion of a liquid crystal display device.

[FIG. 7] A sectional view showing a mounting structure of a liquidcrystal display device.

[FIG. 8] A sectional view showing a fabricating process of an AM-LCD.

[FIGS. 9A and 9B] A top view and a sectional view of an input terminalportion.

[FIG. 10] A top view of a fabricating apparatus.

[FIG. 11] A top view of a fabricating apparatus.

[FIG. 12] A view showing the mounting of a liquid crystal displaydevice.

[FIGS. 13A and 13B] Sectional views showing a mounting structure of aliquid crystal display device.

[FIG. 14] A structural sectional view of an active matrix substrate.

[FIGS. 15A-15F] Views showing examples of electronic equipment.

[FIGS. 16A-16D] Views showing examples of electronic equipment.

[FIGS. 17A-17C] Views showing examples of electronic equipment.

What is claimed is:
 1. A display device comprising: a thin filmtransistor over a substrate, the thin film transistor comprising a gateelectrode over the substrate, a gate insulating film over the gateelectrode; a capacitor wiring line over the substrate, wherein thecapacitor wiring line comprises a same material as the gate electrode; afirst insulating film over the capacitor wiring line; a first conductivelayer over the first insulating film and electrically connected to adrain of the thin film transistor wherein a capacitor is formed betweenthe capacitor wiring line and the first conductive layer with at leastthe first insulating film interposed therebetween; a second insulatingfilm comprising a resin over the thin film transistor and the firstconductive layer wherein at least a portion of the second insulatingfilm has a roughened upper surface; a pixel electrode including areflective conductive film over the second insulating film andelectrically connected to the first conductive layer through a hole inthe second insulating film wherein at least a portion of the reflectiveconductive film has a rough surface due to the roughened upper surfaceof the second insulating film.
 2. The display device according to claim1, further comprising: a terminal portion over the substrate, theterminal portion comprising: a second conductive layer over thesubstrate, the second conductive layer comprising a same material as thegate electrode of the thin film transistor; and a third conductive layerover and in electrical contact with the second conductive layer; and aflexible printed circuit in electrical contact with the terminalportion.
 3. The display device according to claim 1, wherein the pixelelectrode is in contact with the first conductive layer through a secondhole in the second insulating film.
 4. The display device according toclaim 1, wherein the thin film transistor comprises a silicon filmincluding a channel formation region.
 5. The display device according toclaim 1, further comprising a liquid crystal material adjacent to thepixel electrode.
 6. The display device according to claim 1, wherein thefirst conductive layer is electrically connected to the drain of thethin film transistor through the pixel electrode.
 7. The display deviceaccording to claim 1, wherein the reflective conductive film directlycontacts the first conductive layer.
 8. A display device comprising: athin film transistor over a substrate, the thin film transistorcomprising a gate electrode over the substrate, a gate insulating filmover the gate electrode; a capacitor wiring line over the substrate,wherein the capacitor wiring line comprises a same material as the gateelectrode; a first insulating film over the capacitor wiring line; afirst conductive layer over the first insulating film and electricallyconnected to a drain of the thin film transistor, wherein a capacitor isformed between the capacitor wiring line and the first conductive layerwith at least the first insulating film interposed therebetween; asecond insulating film comprising a resin over the thin film transistorand the first conductive layer wherein at least a portion of the secondinsulating film has a roughened upper surface; and a pixel electrodeincluding a reflective conductive film over the second insulating filmand electrically connected to the first conductive layer through a holein the second insulating film wherein at least a portion of thereflective conductive film has a rough surface due to the roughenedupper surface of the second insulating film, wherein the capacitorwiring line and the gate electrode are formed by patterning a firstconductive film.
 9. The display device according to claim 8, furthercomprising: a terminal portion over the substrate, the terminal portioncomprising: a second conductive layer over the substrate, the secondconductive layer comprising a same material as the gate electrode of thethin film transistor; and a third conductive layer over and inelectrical contact with the second conductive layer; and a flexibleprinted circuit in electrical contact with the terminal portion.
 10. Thedisplay device according to claim 8, wherein the pixel electrode is incontact with the first conductive layer through a second hole in thesecond insulating film.
 11. The display device according to claim 8,wherein the thin film transistor comprises a silicon film including achannel formation region.
 12. The display device according to claim 8,further comprising a liquid crystal material adjacent to the pixelelectrode.
 13. The display device according to claim 8, wherein thefirst conductive layer is electrically connected to the drain of thethin film transistor through the pixel electrode.
 14. The display deviceaccording to claim 8, wherein the reflective conductive film directlycontacts the first conductive layer.
 15. A display device comprising: athin film transistor over a substrate, the thin film transistorcomprising a gate electrode over the substrate, a gate insulating filmover the gate electrode; a gate wiring over the substrate, wherein thegate electrode is electrically connected to the gate wiring; a capacitorwiring line over the substrate, wherein the capacitor wiring lineextends in parallel with the gate wiring and overlaps with the gatewiring; a first insulating film over the capacitor wiring line; a firstconductive layer over the first insulating film and electricallyconnected to a drain of the thin film transistor wherein a capacitor isformed between the capacitor wiring line and the first conductive layerwith at least the first insulating film interposed therebetween; asecond insulating film comprising a resin over the thin film transistorand the first conductive layer wherein at least a portion of the secondinsulating film has a roughened upper surface; a pixel electrodeincluding a reflective conductive film over the second insulating filmand electrically connected to the first conductive layer through a holein the second insulating film wherein at least a portion of thereflective conductive film has a rough surface due to the roughenedupper surface of the second insulating film.
 16. The display deviceaccording to claim 15, further comprising: a terminal portion over thesubstrate, the terminal portion comprising: a second conductive layerover the substrate, the second conductive layer comprising a samematerial as the gate electrode of the thin film transistor; and a thirdconductive layer over and in electrical contact with the secondconductive layer; and a flexible printed circuit in electrical contactwith the terminal portion.
 17. The display device according to claim 15,wherein the pixel electrode is in contact with the first conductivelayer through a second hole in the second insulating film.
 18. Thedisplay device according to claim 15, wherein the thin film transistorcomprises a silicon film including a channel formation region.
 19. Thedisplay device according to claim 15, further comprising a liquidcrystal material adjacent to the pixel electrode.
 20. The display deviceaccording to claim 15, wherein the first conductive layer iselectrically connected to the drain of the thin film transistor throughthe pixel electrode.